1. Field of the Invention
The invention relates to a silicon wafer as a raw material of semiconductor devices and a method for producing the same. The invention also relates to a method for growing a silicon single crystal. Particularly, the invention relates to a technology which can provide a silicon wafer in which generation of epitaxial defects is suppressed to a lower number during growth of an epitaxial layer on the wafer.
Priority is claimed on Japanese Patent Application No. 2005-152054 filed May 25, 2005 and Japanese Patent Application No. 2005-204279 filed Jul. 13, 2005, the contents of which are incorporated herein by reference.
2. Description of Related Art
Conventionally, by performing high temperature heat treatment of a p+ type silicon single crystal having resistivity of 0.025 to 0.008 Ω cm, ring likely distributed oxidation-induced stacking faults (ring-OSFs) have been known to occur within the crystal (M. Suhren et al., High Purity Silicon IV, p132, Electrochemical Society, 1996). OSF nuclei are large sized oxide precipitation nuclei which are formed during crystal growth.
Recent studies illuminated generation of epitaxial defects at the corresponding position of ring-OSFs in a p/p+ type wafer comprising an epitaxial layer grown on a p+ type wafer comprising ring-OSFs. Since the epitaxial layer is an active layer for a device, epitaxial defects such as stacking faults and dislocations in the epitaxial layer cause failure of device operation, and result in decreasing yield.
As a conventional solution to the above-described problems, Japanese Patent Application, First Publication No. 2004-165489 (Patent Reference 1) describes a technique in which an epitaxial layer is grown on a wafer sliced from a defect-free crystal in which a ring-like OSF developing region is degenerated in the central portion of the crystal. The OSF developing region is a region at which the ring-OSFs are generated in the crystal during high temperature oxidation.
However, a low pulling rate of a crystal has been required for degenerating the ring-like OSF developing region. Therefore, the technique described in Patent Reference 1 includes a problem of reduced productivity in the manufacturing process of single crystals. In addition, since an extremely narrow range is allowed for rates of pulling defect-free crystals, precise controllability is required to pull a single crystal while controlling the pulling rate within the pulling rate range of defect-free crystals.
An object of the invention is to provide a method for growing a silicon single crystal which is, without reducing productivity, capable of providing a silicon wafer which has a resistivity of 0.025 to 0.008 Ω cm and generates only small numbers of epitaxial defects when an epitaxial layer is grown on the wafer.
The other object of the invention is to provide a silicon wafer of high quality and method for producing the same. The silicon wafer is sliced from the single crystal which is grown by the above-described method for growing a silicon single crystal.
Based on the consideration of the above-described problem on epitaxial defects in p/p+ wafer, an object of the invention is to provide an epitaxial wafer which is produced from a silicon single crystal having a resistivity of 0.025 to 0.008 Ωcm, but is free from generation of epitaxial defects, has a homogeneous in-plane distribution of oxide precipitate density, and has excellent intrinsic gettering property.